Third party coolers are generally better than stock coolers. Cooler Master and Corsair make good coolers. You may choice one as your need, space in the SFF cabinet and budget. But, your existing fan...

The CPU will come with AMD stock cooler fan, and thermal paste should be previously applier to that cooler. You need not to use the existing fan (provided it is not a better third party cooler) and...

From GeForce GT 730 | Specifications | GeForce ....
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If you plan for upgrade the PSU, get a comparatively bigger one, at lease 450-500 watts. VS Series™ VS450 — 450 Watt Power Supply...